Science for All | Why does observing gravitational waves matter? 

The Hindu’s weekly Science for All newsletter explains all things Science, without the jargon.

Updated - July 06, 2023 08:27 am IST

Published - July 05, 2023 01:48 pm IST

An artistic interpretation of an array of pulsars being affected by gravitational ripples produced by a supermassive black hole binary in a distant galaxy, in this handout image released June 28, 2023.

An artistic interpretation of an array of pulsars being affected by gravitational ripples produced by a supermassive black hole binary in a distant galaxy, in this handout image released June 28, 2023. | Photo Credit: Reuters

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Last week, scientists revealed evidence that the universe is constantly flooded with low-frequency gravitational waves, unlocking new avenues to expand our knowledge of the universe.

Albert Einstein’s theory of relativity also predicted the existence of gravitational waves more than a century ago, but the phenomenon was only directly observed in 2016.

What are gravitational waves?

We can define gravitational waves as “ripples” in space-time. Think of it as tiny waves on a lake — the surface seems smooth, but the waves are visible when you get close to it.

In 2016, scientists working with the Laser Interferometer Gravitational-wave Observatory (LIGO) announced that they had detected signals of gravitational waves emanating from two merging black holes, 1.3 billion light years away. Although indirect evidence of the existence of gravitational waves had been discovered from the decaying orbital period of objects called binary pulsars by Russel Hulse and Joseph Taylor in 1974, its direct detection proved difficult until LIGO became operational in 2015.

India’s Giant Metre wave Radio Telescope (GMRT) was one of the six large telescopes worldwide involved in collecting data that led to the recent discovery.

Why is the discovery important?

Observing the information carried by gravitational waves can allow scientists and researchers to analyse parts of the universe that are otherwise practically impossible to see.

Historically, scientists have used electromagnetic radiation in the form of visible light, X-rays, microwaves, ultraviolet light, etc., to study the universe. Gravitational waves function very differently from electromagnetic radiation. Cosmic events, like black holes or neutron stars colliding, generate large amounts of energy as well as gravitational waves. Such events are hard to view at certain wavelengths, but can be studied using information available from analysing gravitational waves.

According to the LIGO official website, gravitational waves can be used to “listen” to the universe, where one would use ears as the primary sensory organ. On the other hand, viewing the cosmos using electromagnetic radiation is like using the “eyes”. “Ear enables you to learn things about the universe that you would never have gleaned from light,” it says.

Black holes, specifically, are places in space with a gravitational pull so strong that even light cannot get away from them. Since it does not reflect light, it is impossible to observe directly using traditional electromagnetic radiation.

Scientists believe that black holes possibly began to form shortly after the universe was born. Hence, studying them can reveal important information about their effects on the universe, especially when it was very young. Researchers are hopeful that “listening” to gravitational waves, can help us understand the creation and evolution of the universe.

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